1. Technical Field
The present invention relates to an apparatus for injecting constant quantitative chemicals. In greater detail, the present invention relates to an apparatus for injecting constant quantitative chemicals which is capable of injecting, without creating particulate contamination, a chemical solution into ultra pure water supplied to a single wafer processing type wafer cleaning apparatus which is used in semiconductor device manufacturing processes, for example.
2. Background Art
As the integration of semiconductor devices has increased, the number of cleaning processes has also greatly increased, and the degree of cleanliness is rapidly approaching that of complete cleanliness. Accordingly, techniques for the clean supply of cleaning solution to cleaning apparatuses are increasingly required.
Currently, cleaning solutions become contaminated during the mixing, dilution, and transport processes, and there are no simple technological countermeasures for preventing this.
The present invention involves the development of a clean chemical solution supply apparatus which is required for wafer cleaning, and contributes to an increase in performance of semiconductor devices by increasing cleaning effects.
In order to accommodate the sub-quarter micron era, which requires an increasing degree of cleanliness, an advance in wafer cleaning apparatuses is first required. In order to completely and uniformly clean a wafer with a large diameter, a process chamber direct connection type single wafer cleaning method is required. Here, new problems occur involving the chemical solution supply system to the process chamber direct connection type single wafer cleaning apparatus.
The conventional chemical solution supply technology involves the "large scale preparation method". In other words, the chemical solution was conveyed by means of a pump from a receiving tank to a dilution and mixing tank, the composition and concentrations were adjusted to specified levels, the solution was then transported by means of a pump from the supply tank through long distance piping, was transported by pump to the storage tank of a wet station, and was supplied to a cleaning tank via a pump and a filter.
In this method, it was not easy to prevent particulate contamination from all the structural components, such as the storage tank, the piping, the joints, the valves, the pumps, the flow meters, the flow regulators, and the like; this problem still has not been solved.
In recent years, a method has been employed for chemical solution supply apparatuses to single wafer processing type cleaning apparatuses in which the cleaning solution is directly supplied to a pure water line. However, the supply apparatus comprises a changeover valve and a mixing zone. Such a structure is inappropriate for the high throughput of single wafer cleaning. In order to achieve the high throughput of the single wafer processing cleaning, it is necessary that the chemical solution supplied to the ultra pure water line be instantaneously mixed with the ultra pure water. Moreover, in the changeover valve method, even if the chemical solution is supplied to the pure water line, time is required for the mixing of the chemical solution and the pure water, and for the changeover. Furthermore, because of the occurrence of particles from the valves, completely clean wafer surface processing is impossible.
A new technology employing capillaries in the chemical solution injecting mechanism has been disclosed in Japanese Patent Application No. HEI 8-21557. By means of this technology, the problem of the instantaneous mixing of the chemical solution and the pure water described above is solved. However, apart from causing the capillaries to simply function as the junction points between the chemical solution and the pure water, there has been no development at the present time with respect to causing such capillaries to operate as system functional elements.